Method of repairing a paper machine dryer journal moisture barrier

ABSTRACT

This invention relates to a method of repairing a moisture barrier separating a paper machine dryer drum from the dryer journal. Such processes of this type, generally, involve filling the cavity between the dryer drum steam intake pipe and the dryer journal with a flowable moisture barrier material. The flowable moisture barrier seals leaks in the dryer journal moisture barrier.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation in part application of Ser.No. 09/571,371, filed May 15, 2000, now abandoned.

BACKGROUND OF THE INVENTION

1 Field of the Invention

This invention relates to a method of repairing the moisture barrierseparating a paper machine dryer drum from the dryer journal. Suchprocesses of this type, generally, involve substantially filling the aircavity between the dryer steam intake pipe and the dryer journal with aflowable moisture barrier.

2 Description of the Prior Art

In conventional paper making machines several large dryer drums orheated cylinders are located near the end of the paper machine. Thedryer drums are conventionally filled with steam at approximately 200 to300 F degrees under pressure. The dryer drums contact both sides of thepaper web and reduce the paper's water content to approximately 5%. Thedryer drums are typically 5 feet wide or wider and typically weigh inexcess of 2 tons. Each drum end is supported by a journal head. Eachjournal head is further supported by a journal assembly at each end.

FIG. 1 is a cross-sectional drawing of a prior art journal assembly 2.The journal assembly 2 acts as an axle to rotate the dryer drum (notshown) about a central axis. The journal assembly 2 typically has ahollow, annular main journal body 3, hereinafter referred to as thejournal. The journal 3 is supported by and rotated via journal bearings4. The bearings 4 are typically located in a housing. U.S. Pat. No. 4,716, 661 by Asman is an exemplary reference of a hollow, annular journalfor a paper machine dryer. Typically the dryer drum steam intake pipe 12is placed into the hollow portion of the journal 3 as shown in FIG. 1.Typically, steam enters into the dryer drum in the direction of arrow A.Typically a steam condensate pipe 8 is located internal to the steamintake pipe 12. In such cases, the steam condensate exits the dryer drumin the direction of arrow B.

A thin annular cavity 16 separates the dryer steam intake pipe 12 fromthe journal 3. This air cavity, primarily, serves as a heat insulatorbetween the dryer steam intake pipe 12 and the journal 3. The cavityeliminates most heat transfer from the steam intake pipe 12 to thejournal bearings 4.

Conventionally a journal moisture barrier 20 is used to prevent steamfrom leaving the dryer drum and entering the cavity 16. Typically, thejournal moisture barrier 20 is an annular flange with a polymericcoating-based material or other moisture barrier, such as a rubbergasket. The journal moisture barrier is typically secured to the journal3 by bolts 21 so that the polymeric coating touches the journal 3.However, conventional journal moisture barriers 20 often fail towithstand the high temperatures of the dryer steam that can reach ashigh as 390° F. Frequently, the journal moisture barrier 20 breaks downor develops a leak that allows moisture from the dryer drum to enter thecavity 16. As high temperature moisture enters the cavity 16unacceptable amounts of heat are transferred through the journal 3 tothe journal bearings 4. High temperature moisture leaks adverselyimpacts the journal 3 and the bearings 4. The moisture can cause thejournal's 3 metal surface too pit and can breakdown the bearing's 4lubrication (not shown) and lubrication system (not shown). Typically aleak in the journal moisture barrier 20 is detected by moisture exitingthe cavity 16 via an opening 14, such a weep hole.

It is known to replace conventional journal moisture barriers 20 whenthey break down or leak. However, this requires many man-hours of laborand downtime for the entire paper machine to replace one moisturebarrier, which ultimately leads to reduced paper production. Anexemplary description of a conventional replacement or repair method isdescribed in U.S. Pat. No. 4, 716, 661, column 4, lines 55-70. A typicalpaper machine includes many dryer journal moisture barriers 20 so thepotential maintenance cost and paper machine downtime is great. Also,simply replacing one conventional journal moisture barrier 20 withanother does not eliminate future replacements. Therefore, a moreadvantageous repair method for damaged journal moisture barriers 20 ishighly desirable.

It is apparent from the above that there exists a need in the art for amethod to quickly and cost effectively repair a paper machine dryerjournal moisture barrier. It is a purpose of this invention to fulfillthis and other needs in the art in a manner more apparent to the skilledartisan once given the following disclosure.

SUMMARY OF THE INVENTION

Generally speaking, this invention fulfills these needs by providing amethod to repair a moisture barrier separating a paper machine dryerdrum from the dryer journal. The air cavity located between the dryersteam intake pipe and the dryer journal is filled with a flowablemoisture barrier. The flowable moisture barrier in the cavity seals anyleaks in the journal moisture barrier.

The above and other advantages, features and benefits of the presentinvention will become more apparent by considering the followingdetailed description and drawings.

A BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a prior art, side, cross-sectional view or a paper machinedryer journal with a conventional moisture barrier; and

FIG. 2 is a side, cross-sectional view of a paper machine dryer journalwith a repaired moisture barrier according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

With Reference to FIG. 2, a leak in the dryer journal moisture barrier20 typically occurs every 6 to 24 months. In order to repair themoisture barrier 20, the entire paper machine must be shut down. In anexemplary embodiment according to the invention, the cavity 16 of FIG.1, which separates the dryer journal 3 from the dryer drum steam intakepipe 12 can be filled with a flowable moisture barrier 18 (FIG. 2). Theflowable moisture barrier 18 seals any damaged areas, such as forexample steam leaks, in the journal moisture barrier 20.

In an exemplary embodiment, the flowable moisture barrier 18 is placedin the cavity 16 (FIG. 1) while the paper making machine is shut down.The repair method according to the present invention is much faster andcheaper than conventional methods. No worker entry into the dryer drumis required and the overall speed of the repair is much greater. Inaddition, if shut down, the papermaking machine can be returned tooperation much sooner than under conventional moisture barrier repairmethods. It is to be understood that the scope of the invention is notlimited to repairs made while the machine is shut down. The inventioncovers filling cavity 16 during machine operation.

The flowable moisture barrier 18 must be able to flow from an opening 14in the cavity 16 such as weep hole 14 or any other cavity opening to thejournal moisture barrier 20. The flowable moisture barrier 18 is ideallypaste-like with a cure time of 1 hour or less. The flowable moisturebarrier 18 must be able to withstand potential temperatures of up to 500degrees F. The cavity opening 14 can be permanently or temporary sealedafter the flowable moisture barrier 18 has been placed in the cavity 16.Exemplary flowable moisture barrier 18 materials include pastes such asPVR manufactured in Luke, Md. In addition the barrier 18 can containfibers, thermosetting organic resins, graphite or Teflon ® basedcompounds containing polytetrafluoroethylene (PTFE).

In order to demonstrate the problem solved by the present invention,temperature readings of several locations of the journal assembly 2, forboth non-leaking and leaking conventional journal moisture barriers 20,were taken, as shown below in the following TABLE.

TABLE Outside Temperature Condition of Journal Temperature of of JournalMoisture Barrier Steam Intake Pipe Bearing Housing 1. Journal MoistureBarrier 251° F. 190° F. not leaking 2. Journal Moisture Barrier 250° F.208° F. leaking

The table displays the temperature at both the outside of the dryer drumsteam intake pipe 12 and the housing of the journal bearing 4 for bothleaking and non-leaking conditions of the journal moisture barrier 20.Item 1 displays the temperature at the two locations when the dryerjournal moisture barrier 20 is not leaking. Item 2 displays thetemperature at the two locations when the dryer journal moisture barrier20 is leaking; i.e. when steam is entering into cavity 16. The journalbearings 4 experiences temperatures over 18 degree higher when thejournal moisture barrier 20 is leaking.

For a journal moisture barrier 20 repaired according to the method ofthe invention, an exemplary temperature difference of 54 degrees wasmeasured between the journal bearing 4 versus the temperature of thesteam intake pipe 12. This temperature was in the range expected for anon-leaking journal moisture barrier as demonstrated in item 1. Therepair according to the invention resulted in acceptable temperatureranges for the journal bearings 4. As discussed above, this reduction inheat at the journal bearing 4 improves the operational efficiency of thejournal bearing 4.

Once given the above disclosure, many other features, modifications orimprovements will become apparent to the skilled artisan. Such features,modifications or improvements are, therefore, considered to be a part ofthis invention, the scope of which is to be determined by the followingclaims.

What is claimed is:
 1. A method of repairing a paper machine dryerjournal moisture barrier comprising the step of substantially filling acavity located between a dryer steam intake pipe and the dryer journalwith a flowable moisture barrier material such that said materialssubstantially covers any damaged areas of the existing journal moisturebarrier.
 2. The method as in claim 1, wherein said flowable moisturebarrier material comprises graphite.
 3. The method as in claim 1,wherein said flowable moisture barrier material comprisesPolytetrafluoroethylene (PTFE).
 4. The method as in claim 1, whereinsaid flowable moisture barrier material comprises thermosetting, organicresins.
 5. The method as in claim 1, wherein said flowable moisturebarrier material is a non-gas at a temperature of less than about 500°F.
 6. The method of claim 1, wherein said flowable material is insertedinto the cavity through the cavity weep hole.
 7. The method of claim 6,wherein said opening is permanently closed after the flowable moisturebarrier is inserted into the cavity.